The present invention relates to the field of coupling optical fibers to optical waveguides; more specifically, it relates to an apparatus and method for manufacturing self-aligned optical fiber to optical waveguide assembles.
There are many applications in optical communications and in optoelectronics where an optical fiber must be connected to an optical waveguide. Connection of an optical fiber to an optical waveguide requires alignment of a face of the optical fiber to the face of an optical waveguide and then bonding of the two faces together. Alignment tolerances of the optical fiber to the optical waveguide must be held to under 1 micron in five degrees of freedom (mutually perpendicular straight X, Y and Z axes as well as a rotational axes about the X and Y axes). The equipment to accomplish this five-fold alignment is expensive and requires a high degree of skill on the part of the person performing the alignment. Five-fold alignment is also time-consuming. Both of these add to the cost of the finished product. Further, with this technique it is extremely difficult or impossible to attach multiple optical fibers to an optical waveguide on very close pitches. An inexpensive method whereby the optical fiber aligns to the optical waveguide would greatly reduce the manufacturing costs of optical communication and optoelectronic devices.
A need therefore exists for an inexpensive method of aligning in the aforementioned five degrees of freedom one or more optical fibers to an optical waveguide.
A first aspect of the present invention is an apparatus for self-aligning an optical fiber to an optical waveguide comprising: an optical waveguide chip including: one or more optical waveguides formed on a first substrate, each optical waveguide having a protruding portion; and one or more alignment rails formed on the first substrate, each alignment rail spaced apart from each optical waveguide by a predetermined distance; and an alignment jig including: one or more grooves formed in a second substrate, each groove adapted to receive one protruding portion and each groove supporting one optical fiber in alignment with one optical waveguide; and one or more alignment grooves formed on the second substrate, each alignment groove spaced apart from the grooves by the predetermined distance and adapted to mate with the alignment rails.
A second aspect of the present invention is an apparatus for self-aligning an optical fiber to an optical waveguide comprising: an optical waveguide chip including: one or more optical waveguides formed on a first substrate, each optical waveguide having a cladding layer extending over a top surface of the first substrate and a protruding portion, the protruding portion including a core portion and a cladding portion; and one or more alignment rails formed on top of the cladding layer, each alignment rail substantially co-planer with the core portion and spaced apart from each core portion by a predetermined distance; and an alignment jig including: one or more trenches in a thick layer on top of a second substrate and one or more grooves formed in the second substrate, each groove open to one trench; each groove adapted to receive one protruding portion and to support one optical fiber in alignment with one optical waveguide; and one or more alignment grooves formed in the thick layer, each alignment groove spaced apart from the grooves by the predetermined distance and adapted to mate with the alignment rails.
A third aspect of the present invention is a method for making a self-aligned connection between an optical fiber and an optical waveguide, comprising: providing a first substrate; forming a first cladding layer on top of the first substrate; forming a core layer on top of the first cladding layer; etching the core layer to form a waveguide core and one or more alignment rails, each alignment rail spaced apart from the waveguide core by a predetermined distance; forming a second cladding on a top surface and on sidewalls of the waveguide core, the waveguide core and second cladding forming a protruding portion of the waveguide, the first cladding layer, the waveguide core and the second cladding forming the optical waveguide; providing a second substrate; forming a mask layer on top of the second substrate; simultaneously etching one or more trenches and one or more alignment grooves in the mask layer, each alignment groove spaced apart from the trench by the predetermined distance and adapted to mate with the alignment rails; etching a groove in the second substrate in each trench, each groove and trench adapted to receive one protruding portion and to support one optical fiber such that a core of the optic fiber aligns with the waveguide core; placing the first substrate onto the second substrate such that the alignment rails engage with the alignment grooves and the protruding portion is received in the groove and trench and placing optical fibers in each trench.